Paper No. 7
Presentation Time: 10:00 AM


WOHL, Ellen, Geosciences, Colorado State University, na, Fort Collins, CO 80523-1482,

Numerous integrative summaries document pervasive human alteration of sediment transport, land cover, ecosystem production, and fresh water distribution, among other landscape characteristics. Legacy effects are ubiquitous, even where not readily apparent. Human alteration of landscapes has implications for understanding and applying concepts of historical range of variability and reference conditions, as well as ecosystem integrity and sustainability and human sustainability. Recent geomorphic research increasingly emphasizes connectivity. River channel connectivity includes lateral, longitudinal, and vertical components. River network connectivity includes landscape, hydrologic, sediment, and riverine components. Connectivity can also be conceptualized as applying to integration across disciplines such as geomorphology, ecology, and social sciences, which share a systems perspective and recognition of the importance of thresholds or tipping points. Tipping points associated with exceedance of regulatory thresholds are relatively easy to identify. Tipping points that represent thresholds between alternative stable states, or the limits of sustainability for a species or for human resource use, are progressively harder to identify. I use the example of beavers to discuss how to identify, predict, and either prevent or force the crossing of tipping points. The common default assumption is that many landscapes have lesser rather than greater human alteration. We need to overcome our own changing baseline of perception and start with the assumption that a landscape has greater rather than lesser alteration, including historical alterations that continue to influence the landscape. I suggest that geomorphologists emphasize: historical context; integrated ecosystem management; and quantifying thresholds and ecosystem resilience. This forward-looking approach emphasizes management and pathways to protect and/or restore desired conditions.